Johnny Carson was both one of the best- and least-known figures in 20th century popular culture, which is partially why his life and career still fascinate us seven years after his death.

Carson really was the "King of Late Night," but despite multiple documentaries and biographies of the late host of "The Tonight Show," we still ponder what made him so great on TV and what tortured him so deeply when the studio lights went black.

The answers to those questions may be found in the superb, exhaustive and, in the end, touching two-hour "American Masters" film by Peter Jones, "Johnny Carson: King of Late Night," airing Monday on PBS. It's hard to watch this extraordinarily insightful film without realizing that for all the happiness Carson gave to millions during his 30 years on NBC, the offstage Carson was haunted by complicated inner demons his entire life.

Jones, whose previous work includes "Stardust: The Bette Davis Story" and "Inventing LA: The Chandlers and Their Times," appropriately references "Citizen Kane" in structuring his film, which opens and closes deep in an underground storage facility in Kansas where hours and hours of "The Tonight Show Starring Johnny Carson" tapes are stored.

Enigmatic life

While other filmmakers have referenced "Kane," the links have often felt convenient. But the device works with uncanny perfection with Johnny Carson, right down to the enigma of the "Rosebud" in the life of the Iowa-born, Nebraska-reared boy who vied with his older sister and younger brother for their mother's attention. As a teenager, he turned to magic tricks as a way of drawing attention to himself while, at the same time, adopting a kind of sleight of hand about the disappointment and loneliness that would define him into adulthood.

Carson's "Rosebud" was a book called "Professor Hoffman's Modern Magic" and he was soon entertaining others with deftly executed magic tricks as "The Great Carsoni." After the Navy and college, he began his career at WOW radio and TV in Omaha, where he hosted a morning show called "The Squirrel's Nest."

Carson and the medium of TV grew up together. In the early years, many TV shows and stars were recycled from radio, including two of Carson's idols, Jack Benny and Red Skelton. NBC created "The Tonight Show" in 1953, first hiring Steve Allen as the host and then the mercurial, more cerebral Jack Paar. When Paar quit in 1962, the network eventually turned to the young host of the game show "Who Do You Trust?" to take over. Carson's name later became part of the title of the show he hosted until 1992.

Off camera, he married four times, battled alcohol off and on until the end of his life, was a "cheap drunk" who could turn violent after only a couple of drinks, berated himself for being a detached and inadequate father to his three sons, cheated on all of his wives, and, most of all, spent his entire life trying in vain to please his mother.

Withholding approval

Ruth Carson was a gregarious woman with a keen sense of humor, but no matter how famous her middle child became, she always seemed to withhold approval. At one point, she watched a Carson monologue with a reporter and, when it was over, dismissed it as "not very funny."

After Ruth Carson died, her family found a box in her bedroom containing newspaper clippings about Johnny's career going back to his early days in show business. Carson kept the box in his closet for the rest of his life.

Millions of American TV viewers never saw any of this, of course. Instead, they saw a comic genius who had learned perfect timing from the master himself, Jack Benny, and who managed to make even the most overexposed Hollywood personality seem interesting.

While adding dimension to what we know of Carson's personal life, "King of Late Night" is rich with testimony to Carson's professional greatness in the form of clips from the shows themselves. Slightly naughty with Raquel Welch and Dolly Parton, reacting with a deadpan stare into the camera as one of Joan Embery's marmosets urinates on his head, cracking up as he's entrapped by Rickles' comic firecrackers, Carson is the master magician of television.

"King of Late Night" is a celebration of one man's life and career. To older viewers, it's a reminder of all those late nights of the past, and to younger viewers, a tantalizing revelation of an Olympian talent who is as funny and engaging today as he was decades ago.

It's said that every TV host who's come along after Carson owes him a debt. If so, it's a debt likely to remain unpaid for all time. "King of Late Night" offers ample evidence why.